Device for contour dressing grinding wheels



5, 1952 J. c. GARAND 2,584,121

DEVICE FOR CONTOUR DRESSING GRINDING WHEELS Filed Jan. 29, 1948 5 Shets-Sheet 1 John .E. Elnrund Feb. 5, 1952 J. c. GARAND 2,584,121

DEVICE FOR CONTOUR DRESSING GRINDING WHEELS Fi led Jan. 29, 1948 5 Sheets-Sheet 2 gwuc/wto u John Elnrnnd 5 sheets-sa a :5

Feb. 5, 1952 J. c. GARAND DEVICE FOR CONTOUR DRESSING GRINDING WHEELS Filed Jan. 29, 1948 Jul-Ln El Burn-11d Z' LWY W 1952 J. c. GARAND 2,

DEVICE FOR CONTOUR DRESSING GRINDING WHEELS Filed Jan. 29, 1948 5 Sheets-Sheet 4 IwvEv -E Feb. 5, 1952 J. c. GARAND 2,584,121

DEVICE FOR CONTOUR DRESSING GRINDING WHEELS Filed Jan. 29, 1948 5 Sheets-Sheet 5 Jmhn E. Elurund Patented Feb. 5, 1952 DEVICE FOR CONTOUR DRESSING GRINDING WHEELS John C. Garand, Springfield, Mass., .assignor to the United States of America as represented by the Secretary of War Application January 29, 1948, Serial No. 5,156

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

The invention described in the following specification and claims may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a device for dressing the grinding wheel of an automatic grinding machine to a desired contour.

In the manufacture of small arms as well as other articles of manufacture, it is frequently necessary to grind a component to a finished dimension having but a minute manufacturing tolerance. While automatic grinding machines for grinding cylindrical objects have been developed that automatically advance the grinding wheel slightly after completion of a grinding operation in order to dress the wheel in preparation for grinding of a new component, such machines do not produce the accuracy required "in certain specific applications. This applies particularly to diametra-l dimensions involving mating parts where close fits are required. One such example may be found in the gas cylinder and cooperating piston arrangement for agas operated firearm, such as is employed in the U. S. Rifle, cal. .30 M1. In this rifle the piston diameter must be ground to within .0005 of a certain dimension and also the length of such piston must be held to .a ccrtain'minimum dimen- 'sion.

As is well known in the grinding art, the wheel used for grinding an article of manufacture is rapidly dulled after a short period of use. Obviously a dull cutting tool will not and can not consistently remove metal from thearticle 'being worked upon and continue to maintain accuracy of a very high order. It is therefore necessary to dress the wheel after grinding each component.

Accordingly it is an object of this invention to provide "a device for accurately dressing a grinding Wheel to a desired contour.

Another object of this invention is to provide a device for dressing a grinding wheel whichcan then accurately grind simultaneously the diameter and length of a-work piece.

A'specific object of this invention is to provide a "device for dressing a grinding wheel to a desired contour which will automatically grind the piston of the U. S. Rifle, cal. .30 M1 to the required diameter and length. I

The specific nature of the invention as well as other "objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is ,a perspective view of the device utilized for contour dressing grinding Wheels of an automatic grinding machine.

Fig. 2 is a cross sectional view taken along the line '22 of Fig. 3.

Fig. 3 is a top view of Fig. 51.

Fig. 4 is a sectional :view taken along the line 4-41 of Fig. 3.

Fig. 5 is .a front elevational view of the device.

Fig. 6 is a .view taken along the line 6-.-6 of Fig. 5.

Fig. 17 is an enlargedcross-sectional view taken along the line .'l! of Fig. -6.

Fig. 8 is a cross-sectional view taken along the line 8-43 of Fig. 3.

Fig. 9 is a :front elevational view of the apparatus utilized to hold and rotate the work piece.

Briefly this invention comprises a diamond holder slidably mounted within a housing and such housing is in turn supported by a resilient .U-shaped base. The housing supporting the diamond holder :is arranged to be held in cutting relationship with the grinding wheel of a conventional grinding machine through the bias .of .the resilient base and is also arranged to fol- :low :the contour of the wheel cutting surface by means of a lever arrangement secured to the housing. A template is associated with such lever arrangement and reciprocating m vement of the table on which the grindin wheel dressing device is mounted provides the motivating force for actuating the lever arrangement {to produce movement :of the diamond ..:holder in accordance with the contour of the template.

There is shownin Fig. 4 :a cross-sectional .view .of the grinding wheel contour dressing device of this invention in assembled relation. .a'Ihe .device is shown mounted .on a longitudinally movable table ll! of an automatic grindingmachine (not shown). Table H1 is arranged to reciprocate a limited amount .on the bed .of the grinding machine in order to pass the work :and thediamond over the cutting suriace .of a grinding wheel '38 as will be later explained. The device comprises a' base 84, a cylindrical diamond holder H, a substantially rectangular housing 12 which supports diamond holder I1, and a resilient base member 13. Base l3 comprises a U shaped member preferably formed of spring steel and is secured to base 84 :by a block 42 and screws 44. Housing 1'2 is secured between the upright arms :of base [3 by screws iii. The front armof base member 13 is suitably bifurcated as best shown at 86 in Fig. 3 in order to straddle a *reduced frontend portion 81 of hous- 3 ing |2 which protrudes from the body portion thereof as best illustrated in Fig. 1. The housing I2 is provided with a horizontally disposed hole |4 which-is. doubly counterbored on one end thereof as, shown .at l5 and IS. The other end of hole I4 is counterbored as shown at l! and a bearing member 18 is inserted therein.

Diamond holder is a cylindrical member and is provided with an integral head l9 of enlarged diameter. A suitably mounted diamond 31 is secured within a longitudinal recess (not shown) in the other end of holder 1|. A sleeve 20 is fixedly inserted in counterbore l6 and holder Ii is placed in hole |4 so that head |9 thereof rests within sleeve 20 while the other end containing diamond 31 projects out of bearing l3. Holder II is so located within housing l2 that diamond 31 will be below the work pieceto be worked on. A spring 2| is placed within counterbore in surrounding relationship with holder I. The free end of spring 2| bears against the shoulder produced by head 19 to bias holder I I rearwardly. Head W of holder II is bifurcated as shown at 85 to receive a cam member 22 which is'utilized to move holder longitudinally in a manner as will be presently described. Cam member 22 is pivotally secured to holder 'II by a transverse pin 23. Pin 23 engages a transverse hole 24 provided near the forward end ofcam member 22. The extreme forward end of member 22 is arcuate in shape as shown at 26 and terminates in a hook-like portion 2'! arranged to extend'within a longitudinal slot 28 provided in sleeve 20. Such hook-like portion engages the rear end surface of slot 28 and acts as a lever arm with pin 23 as the fulcrum. As cam member 22 is pivotally secured to holder II and sleeve is fixedly secured within housing l2, counter-clockwise movement of such member will thereby force holder II to move forwardly against the bias of spring 2|. Clockwise rotation of cam member 22 will, of course, permit rearward movement of holder H and thereby of diamond 31 relative to housing I2.

Cam member 22 is pivoted about pin 23 by a screw which contacts the rear end of such member. Such screw is vertically supported in a cylindrical boss-like member 29 integrally formed on top of housing l2 and is manually rotated by a cap 30 which is secured to the top of screw 25 by means of a nut 3|. A plurality of vertically disposed serrations 32 are evenly disposed about the interior of cap 30. Such serrations are engageable by a detent 33 supported within a horizontally disposed hole 34 in boss 29.

A spring 35 biases detent 33 outwardly into yielding engagement with serrations 32. Serrations '32 may be so spaced as to provide a microscopically fine adjustment of diamond holder M if so desired.

An actuating lever 36 is pivotally secured to housing l2 by means of a depending stud 39 E'se'cured by brazing to the underside of housing -|2.' :The end of lever 36 pivotally secured to stud 39 is arcuately shaped as shown at 40. A fulforum member 4| is secured to block 42 by a screw 43'. The fulcrum member 4| is engageable with lever 35 near the arcuate 'end thereof for a purpose to be later described. A carbide insert (not shown) is preferably secured to lever 36 where fulcrum member 4| contacts such lever.

V A template 45 is secured, as by brazing, to the side of lever 36 and near the free end thereof.

Template 45 has a' profile which is desired to be reproduced on the cutting surface of grinding wheel 38 and such template is prefera lrm d 0f 4 a carbide material. A bar 46 provided with a tracer member 41 which is engagcable with template 35 is longitudinally mounted on the bed of the grinding machine (not shown) as shown in Figs. 5 and 6 by a bracket 48. Bar 46 rests on a stepped cylindrical bearing plug 33 which is rotatably secured to table If! and is provided to rigidly back up tracer point 41.

Grinding wheel 38 forms a part of the grinding machine (not shown) and is rotatably mounted thereon within a transversely slidable hydraulically operated head. Wheel 38 is arranged to be automatically advanced into the work piece incrementally after each grinding cycle by amounts as small as .0001" and such Wheel may be rapidly moved away from the Work piece when the grinding operation has been completed to permit insertion of another piece because of the transversely slidable head just 12 by a plurality of screws E3.

referred to.

To illustrate the manner of use of the grinding wheel contour dressing device herein described a piston 50 of the U. S. Rifle, cal. .30 M1 is chosen as a specific example of an article to be ground to size by a grinding wheel shaped in accordance with the teachings of this invention. Such piston is shown in Fig. 9 and comprises a head portion 62 and arod portion 63 joined by a tapered section 64. The problem in thisspecific illustration is to grind the diameter of head portion 52 to a prescribed dimension within a manufacturing tolerance of .0005" while maintaining the length of such head portion from the face thereof to the start of tapered section 64 also to a prescribed dimension. Template 45 is shaped to the contour shown for the cutting surface of grinding wheel 38. A chuck 5| is provided to hold the piston 50 while being worked on and such chuck is rotatably supported in a headstock 35 which is suitably secured to table lil. A bracket 66 mounted on top of headstock 65 supports an electric motor 81 and chuck 5| is rotated by a belt drive 68. An operating handle 69 is associated with chuck member 5| to close the jaws of the chuck.

To position head portion 82 of piston 50 when such piston is secured within chuck 5| so that the head portion ofthe piston will be opposite the cutting surface of grinding wheel 38, a stop member 54 is provided. Such stop comprises a screw 55 having an integral head portion 56 to facilitate manual adjustment of such screw. Screw 55 is threadably mounted on a bracket 52 and may be locked therein by any conventional device. Such bracket is secured to housing |2 by screws 53 as shown in Figs. 1 and 3.

While grinding piston 53 it is convenient for the operator to know whether such piston has been ground to the required dimension without the necessity of manually measuring the diameter and also to have a means for indicating whether the piston is being ground truly concentric. Accordingly, there is provided a dial indicator 5? to provide such indication. Indicator 5'! is vertically mounted in a bracket 58. Bracket 53 is mounted alongside of housing l2 and is secured to block 32 as shown in Fig. 1. A plunger 15 connected to dial indicator 51 for actuation of the needle therein (not shown) projects downwardly out of bracket 58..

An L-shaped arm H is secured to a flat spring Spring 12 is in turn vertically secured to a block 74 by screws '15 and such block is secured to base 84 by brazing endof arm 1 l, as-shown inFigs. 1, 3 and 14, there is secured an upstanding bracket :15. .Such bracket is secured by a screw l1 engaging an elongated .slot .18 to permit limited. adjustment of bracket 16. An integral arm-like feeler member. 19 is horizontally disposed on top of bracket 15 and is provided to contact piston 53. On the end of arm member H which is substantially adjacent to plunger 15, there is "mounted a flat spring 83. A protective finger-like piece 8] is placed on top of spring 86 and such piece and spring 80 are secured to arm 11 by a screw'B2. A vertically disposed hole 83 is provided on the end of piece 8| of somewhat greater diameter than plunger to permit plunger .10 to pass therethrough and contact spring 83.

.Feeler member 19 is arranged to contact piston 53 and dial indicator 5? is preferably adjusted to read zero when the diameter of piston 51) has been ground to the required dimension. Any change in this dimension results in forcing :feeler member 79 to move towards or. away from the axis :of piston 55 so that spring [2 is flexed and thus forces arm .7 i to pivot slightly. Such pivoting movement moves spring 80 thereby producing a change in the reading of dial indicator 5! and thus indicating changes in diameter .of the piston 59 :as it is being ground as well as the finished diameter. t

Operation Piston 50 is inserted in chuck 5!. with the front face of such piston contacting theend of stop member 54 which has been previously adjusted to insure that piston 50 will be properly centered on wheel 38. As the jaws of chuck 5| are tightened by means of handle '69, piston. 50 is drawn out of contact with the end of adjusting screw 55. Prior to inserting piston 53 in chuck 5|, grinding wheel 38 is pivoted away from its operating position as mentioned above. Adjusting cap 36 is then manipulated to position holder I l and thereby diamond 31 so that grinding wheel 33 will be dressed as soon as the diameter and length of piston 53 have been ground to the desired dimensions.

As table ii] reciprocates longitudinally on the bed of the grinding machine (not shown), template 45 of lever 35 rides along tracer point 41. Changes in the contour of template 45 contacted by tracer 4! forces the lever38 to be pivoted about stud 39 in accordance with the changes in contour of template 45. As fulcrum member M, which is secured to block 42, is fixed relative to lever 36, any movement of such lever will produce a transverse movement of the device.-. As :base member I3 is in the form of a U-shaped spring, such base member will beflexed outwardly away from the grinding wheel when the template end of lever 33 is moved inwardly. The housing l2 containing the diamond holder H is moved an amount proportional to the movement of lever .36. Once piston 50 has been ground to the desired dimensions, grinding wheel 38 comes into contact with diamond 3 As housing I2 .moves to the right from the position indicated in Fig. '3, template 45 also moves to the right and rides along fixed tracer member 41. Since member 4| has been adjusted so that tracermember 41 continually pivots lever 36 forwardly about the fulcrum point of member 4| regardless of the contour of template 45, it will be readily apparent that housing I2 is constantly forced to the rear away from grinding wheel .38 thereby flexing the resilient arms of base member 13. Thus, when template 45 decreases in contour, the bias of the 6 arms of base member l3 will continue to maintain the contact between template and tracer member thereby moving housing I2 forwardl to keep diamond 3'! in dressing contact with grinding wheel 38. As table it continues to move to the right, the contour of template 45 is increased, as shown in Figs. 3 and-6, and thus lever 36 is pivoted so as to retract housing l2 to the extent necessary for diamond 3'! to follow the contour of the-cutting surface of grinding wheel 38. The return movement of table It to the left will actuate diamond3l .in a manner converse to that describedfor movement to the right.

In addition to dressing grinding wheel '38, the device of this invention also serves to limit the amount of metal which will beground off of pieton 50. Since diamond 31 is adjusted to protrude from housing 1'2 so 'as to begin dressing grinding wheel 38 as soon as piston is ground to size, any further undesirable advance of wheel 38 toward piston will be nullified by the dressing action of diamond 31. This correct position of diamond 31 as well as the necessary adjustment to compensate for wear is obtained by rotating cap 35 which in turn rotates screw 25. This movement rotates cam member 22 about pin 23 and the hook portion 21 of such cam member being in contact with the rear end surface of slot 28 of sleeve 25 forces holder H and thereby diamond 31 forwardly the desired amount. The bias of spring 2| maintains hook portion 2! of cam member 22 in contact with sleeve 20 at all times so that the other end of such lever is maintained in contact with screw 25. g

If it is desired to change the location of the dressing movement of diamond point 31 in a direction parallel to the longitudinal axis of table it in order to properly initiate such movement in accordance with the .desired contour of wheel 38, it is merely necessary to free bar 46 from bracket 48 by loosening screws 59 in order to relocate tracer point 41 along a line parallel to the longitudinal axis of table It at the point where the pivoting movement of lever 36 will effect contact of diamond 3'! with grinding wheel 38 in accordance with the form of template 45, whereupon screws 53 are again tightened, suitable slots '50 being provided to permit such adjustment of bar 46.

From the foregoing description it is clearly apparent to those skilled in the art that there is here provided a device for contour dressing the grinding wheel of a grinding machine to permit accurate grinding of an article of manufacture to within exceedingly close manufacturing tolerances. The device herein described is of simple construction and is positive of action. Any readjustment of the diamond point can be conveniently and positively made thereby insuring that the diamond will dress the wheel to assure accuracy in grinding the component.

in addition to the foregoing, the dial indicator for indicating the correct diameter of the ground piston is a quick and convenient means for notifying the operator whether such piston is acceptable and still further such device eliminates the need for any manual gaging of the piston which greatly simplifies the grinding operation thereof.

Iclaim:

.1. In a grinding wheel dresser having a resilient U-shaped base member and a housing secured to the open end thereof, a cylindrical dressing tooltholder slidably mounted in the housing and having a bifurcated rear end porition of enlarged diameter, spring means carried in the housing and arranged to surround said tool holder forwardly of and adjacentto said enlarged diameter portion whereby said tool holder is normally biased rearwardly into the housing, a lever pivotally secured to said tool holder and arranged to lie within said bifurcated portion thereof, said lever having an arcuate front end terminating in a rearwardly extending, hook-like portion, a sleeve fixedly secured within the housing and arranged to surround said rear end portion of said tool holder, said sleeve having a slot therein for receiving said hook-like end of said lever, and screw means extending into the housing and through said sleeve in contact with the rear end of said lever, and all adapted and arranged whereby the advance of said screw means against the rear end of said lever pivots said hook-like end against said sleeve thereby forcing said tool holder forwardly against the bias of said spring means.

2. In a grinding machine having an abrasive wheel for simultaneously grinding the diameter and length of a work-piece, a device for dressing the Wheel comprising, in combination, a housing arranged to reciprocate in a direction parallel to the peripheral surface of the wheel, a cylindrical tool holder slidably mounted in said housing and arranged to fixedly receive a diamond dressing tool, said tool projecting forwardly from said housing in position to dress the wheel upon completion of grinding the work to the required dimensions, said tool holder having a bifurcated rear end portion of enlarged diameter, spring means in said housing arrangedto surround said tool holder and disposed forwardly of and in abutting relationship with said enlarged diameter portion for normally biasing said tool holder rearwardly into said housing, pin means in said tool holder extending across said bifurcated portion, a lever pivotally mounted in said bifurcated portion on said pin means, said lever having an arcuate front end terminating in a rearwardly extending hook-like portion, a sleeve fixedly secured within said housing and arranged to surround said bifurcated portion of said tool holder, said sleeve having a longitudinal slot therein for receiving said hook-like end of said lever, screw means extending into said housing and through said sleeve to contact the rear end of said lever, a rotating cylindrical cap'fixedly secured to the upper end of said screw means, a plurality of vertically disposed serrations equally spaced about the interior surface of said cap, and spring-biased detent means disposed in yielding engagement with said serrations for obtaining increments of rotation of said screw means, all adapted and arranged whereby rotation of said screw means in one direction pivots said lever about said pin means and against said fixed sleeve to advance said tool holder and thereby said diamond forwardly, said spring means being arranged to bias said tool holder rearwardly into the housing upon rotation of said screw means in the opposite direction whereby the existence of backlash in said screw means is eliminated.

3. In a grinding machine, a grinding wheel having a stepped grinding surface, a table slidably mounted on the machine and arranged to reciprocate transversely of said grinding surface on said wheel, and a device for dressing said grinding wheel comprising a base member mounted on said table and having a pair of upstanding resilient spac'ed-apart arms, ahousing disposed between said arms and fixedly secured to the upper ends thereof, a tool holder mounted in said housing for receiving a diamond dressing tool, an actuating lever pivotally secured at one end thereof to said housing, template means fixedly secured to the other end of said lever, and a tracer member fixedly secured to the grinding machine in the path of the reciprocating movement of said template means whereby said lever is pivoted to actuate said housing for moving said dressing tool into contact with said grinding surface on said wheel in accordance with the contour of said template means.

4. In a grinding machine, a grinding wheel having a stepped peripheral grinding surface, a table slidably mounted on the machine and arranged to reciprocate transversely of said grinding surface on said wheel, and a device for dressing said grinding wheel comprising a base member mounted on said table, a pair of resilient arms projecting upwardly from said base member, a housing disposed between said arms and fixedly secured to the upper ends thereof, a tool holder slidably mounted in said housing and adapted to fixedly receive a diamond dressing tool, an actuating lever pivotally secured at one end thereof to the underside of said housing, template means fixedly secured to the other end of said lever, said template meanshaving a contour converse to that of said grinding surface on said Wheel, a tracer member fixedly secured to the grinding machine inthe path of the reciprocating movement of said template means, a plate fixedly mounted on said base member between said resilient arms, and fulcrum means mounted on said plate forwardly of said lever for contact therewith whereby the pivoting movement thereof is conversely transmitted to said housing, said dressing tool being thereby actuated to follow the contour of said grinding surface on said wheel.

5. In a grinding machine having a contoured grinding wheel and a table arranged to reciprocate transversely of the grinding periphery of the wheel, a device for dressing the wheel comprising a base member fixedly secured on the table, a pair of resilient arms projecting upwardly from said base member, a housing disposed between said arms and fixedly secured to the upper ends thereof, said housing having a reduced portion extending forwardly therefrom through the foremost of said resilient arms, a diamond dressing tool fixedly mounted in said reduced portion and projecting forwardly therefrom to contact the grinding periphery of the wheel, a stud pro jecting downwardly from the underside of said housing, an actuating lever having one end thereof pivotally engaged with said stud, a template fixedly secured to the free end of said lever and having a contour converse to that of the grinding wheel, a tracer member fixedly secured to the grinding machine in the path of movement of said template, a fulcrum member, and screw means fixedly mounting said fulcrum member on said base member forwardly of said depending stud on said housing, said fulcrum member having a rearwardly projecting angular surface arranged to form a fulcrum point for contact by said lever whereby movement of the free end thereof toward the grinding wheel moves said housing rearwardly against the bias of said resilient arms of said base member in accordance with the contour of said template, said fulcrum member having an elongated slot therethrough for passage of said screw means whereby the location of said fulcrum on said base member is adjustable toward or away from the periphery-of the grinding wheel in' order to control the ex I 9 tent of movement imparted by said lever to said housing and thereby to said dressing tool.

6. The combination defined in claim 5 including a bracket fixedly secured to the grinding machine adjacent the side of the reciprocable table, and screw means fixedly mounting'one end of said tracer member to said bracket,said tracer member having elongated slot means therethrough for passage of said screw means whereby the location of said tracer member is longitudinally adjustable relative to said template for correlating the initiation of the dressing action of said diamond with the beginning of the peripheral contour of the grnding wheel.

JOHN C'. GARAND.

- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Name Date Weindel Oct. 16, 1883 Stevens Mar. 22, 1910 Johnson Oct. 11, 1910 White Sept. 29, 1914 Olson Mar. 19, 1918 Maickel June 24, 1930 Scusa Feb. 10, 1931 Wainwright Apr. 8, 1941 Foster Jan. 20, 1942 Pollard Feb. 13, 1945 La Pointe July 15, 1947 Barnes Feb. 24, 1948 Klukan Oct. 12, 1948 FOREIGN PATENTS Country Date Great Britain Nov. 1, 1934 

